Practical total synthesis of (.+-.)-aklavinone and total synthesis of aklavin

Ferrier/Aza-Wacker/Epoxidation/Glycosylation (FAWEG) Sequence to Access 1,2-Trans 3-Amino-3-deoxyglycosides

3-Amino-3-deoxyglycosides constitute an essential class of nitrogen-containing sugars. Among them, many important 3-amino-3-deoxyglycosides possess a 1,2-trans relationship. In view of their numerous biological applications, the synthesis of 3-amino-3-deoxyglycosyl donors giving rise to a 1,2-trans glycosidic linkage is thus an important challenge. Even though glycals are highly polyvalent donors, the synthesis and reactivity of 3-amino-3-deoxyglycals have been little studied. In this work, we describe a new sequence, involving a Ferrier rearrangement and subsequent aza-Wacker cyclization that allows the rapid synthesis of orthogonally protected 3-amino-3-deoxyglycals. Finally a 3-amino-3-deoxygalactal derivative was submitted for the first time to an epoxidation/glycosylation with high yield and great diastereoselectivity, highlighting FAWEG (Ferrier/Aza-Wacker/Epoxidation/Glycosylation) as a new approach to access 1,2-trans 3-amino-3-deoxyglycosides.

Doxorubicin and Aclarubicin: Shuffling Anthracycline Glycans for Improved Anticancer Agents

Anthracycline anticancer drugs doxorubicin and aclarubicin have been used in the clinic for several decades to treat various cancers. Although closely related structures, their molecular mode of action diverges, which is reflected in their biological activity profile. For a better understanding of the structure-function relationship of these drugs, we synthesized ten doxorubicin/aclarubicin hybrids varying in three distinct features: aglycon, glycan, and amine substitution pattern. We continued to evaluate their capacity to induce DNA breaks, histone eviction, and relocated topoisomerase IIα in living cells. Furthermore, we assessed their cytotoxicity in various human tumor cell lines. Our findings underscore that histone eviction alone, rather than DNA breaks, contributes strongly to the overall cytotoxicity of anthracyclines, and structures containing N,N-dimethylamine at the reducing sugar prove that are more cytotoxic than their nonmethylated counterparts. This structural information will support further development of novel anthracycline variants with improved anticancer activity.

Gold-catalyzed tandem Diels–Alder reactions of enynals/enynones with alkenes: generation and trapping of cyclic o-QDMs

Gold-catalyzed generation of the highly reactive cyclic o-QDM species and application in preparation of structurally unique propeller-like molecules.

Tautomerism in 11-hydroxyaklavinone: a DFT study

The antharquinone-based chromophore of 11-hydroxyaklavinone is present in the structure of an anticancer agent, daunomycin. On the other hand, aklavinone is the parent aglycone of certain anthracycline antibiotics that possess anti-cancer activity too. The structures of aklavinone and its 11-hydroxy derivative have many –OH groups, and two keto groups which may take place in certain tautomeric equilibria. Of these tautomeric forms, presently the one involving the anthraquinone based tautomers of 11-hydroxyaklavinone has been investigated quantum chemically in the framework of the density functional theory at the levels of RB3LYP/6-31G(d) and RB3LYP/6-31G(d,p).

Total synthesis of (+/-)-murrayazoline

The total synthesis of (+/-)-murrayazoline (1) is described. The characteristic hexa-heterocyclic structure of 1 was constructed by a combination of the intramolecular Friedel-Crafts-type Michael addition and Pd-catalyzed C-O coupling reactions. The N-substituted carbazole component was synthesized in one pot by the double N-arylation of a sterically hindered amine with a dibromobiphenyl derivative.

Regioselectivity of Rhodium Nitrene Insertion. Syntheses of Protected Glycals of l-Daunosamine, d-Saccharosamine, and l-Ristosamine

[reaction: see text] The carbamate-protected glycals of naturally occurring 3,4-cis-3-amino-2,3,6-trideoxyhexoses (l-daunosamine, d-saccharosamine, and l-ristosamine) were prepared from noncarbohydrate starting materials. The short, high-yield syntheses are based on the chemoselective insertion of a rhodium nitrene in an allylic C-H bond rather than in a C-H bond that is alpha to an oxygen substituent.

A ring-closing metathesis approach toward formal total synthesis of (+)-diplodialide A

An asymmetric formal total synthesis of diplodialide A 1a has been achieved starting from methyl acetoacetate 6 and (R)-3-buten-2-ol 7. The macrocyclic ring core of (+)-diplodialide A 1a was constructed, in an excellent yield, by using a ring-closing metathesis strategy.

Skeletal diversity via a branched pathway: efficient synthesis of 29 400 discrete, polycyclic compounds and their arraying into stock solutions

We report the synthesis and arraying of 29 400 structurally diverse and complex polycyclic carbocycles using diversity-oriented synthesis (DOS) and the "one bead-one stock solution" technology platform. Skeletal diversity, a difficult challenge in DOS, was achieved with a branching reaction pathway using one or two Diels-Alder reactions. This pathway yields small molecules having 10 different skeletons.

Efficient synthesis of functionalized furans via ruthenium-catalyzed cyclization of epoxyalkyne derivatives

Ruthenium catalyst TpRuPPh(3)(CH(3)CN)(2)Cl is found to effect the cyclization of epoxyalkynes to furans in the presence of Et(3)N. The reactions worked well for various epoxyalkynes with suitable oxygen and nitrogen functionalities with low loading of catalyst. It failed with disubstituted epoxyalkynes. The mechanism was elucidated by a deuterium labeling experiment that suggested that the mechanism involved a ruthenium-vinylidenium intermediate.